The present invention relates to mixed nitrides in films having at least two metals, in particular for coating tools and product components subject to extremely heavy wear, with the metals having a markedly different melting point. Mixed nitrides, in this case, referring to a solid solution between its different components. In addition, this invention relates to the associated method or process for manufacturing such mixed nitride films by depositing of metal alloy targets by means of an arc with the simultaneous addition of nitrogen as a reaction gas.
The application of conventional physical vapor deposition, PVD, coating methods as wear protection on tools has so far been remarkable success. The coating system, the techniques of which have been fully developed today for these applications, namely TiN, is, however, not yet suited to offer a complete solution for all wear problems. The number of hard substances with comparable hardness values is extraordinarily large. Since these hard substances have to some extent be metallic, covalent or ionic bonding character, they are, in general, very different with respect to their chemical, electrical, thermal and/or mechanical properties. In many instances, these known hard substances can also be combined or even mixed.
In particular mixed films or multilayer-films would within one single film of a few microns (.mu.m) permit division of functions between the film surface, which must be as hard as possible and with respect to the material to be worked or the adjoining medium chemically stable at the working temperature, and the film adjoining the carrier material, which should have high chemical affinity for this material and comparable thermal coefficient of expansion and E-module in order to permit optimum adhesion even under heavy use or wear and tear.
With chemical vapor deposition, CVD, methods, the manufacture of graded films is already used on a commercial scale for coating hard metal indexable inserts. In this method the film concentration is regulated by way of concentration changes of the used gases, however, with comparatively high reaction temperatures being required for the process. At 1000.degree. C., however, the working temperatures are far too high for many precision parts, in particular for those of tool steels, so that the resulting form changes exclude broad-range general application. The PVD methods, which can be used at low temperatures, in particular cathode sputtering methods require, by contnrast, either for each concentration a source with graded alloy proportions or a part to be coated, the geometric position of which needs to be changed with respect to several different material sources. This method is not very useful for practical applications.